Some 3D imagers exist today. An example of such a prior art is WO-2009139971 (A2), entitled “COMPUTER VISION-BASED MULTI-TOUCH SENSING USING INFRARED LASERS”. Another patent application US-A-2002033818, entitled “Three-dimensional relative positioning and tracking using LDRI” teaches the use of a laser to illuminate a target and then to acquire an enhancement of the imagery produced on the basis of such an illumination. Such 3D imagers are also described in a textbook entitled ‘Principles of 3D image analysis and synthesis’, Bernd Girod, Günther Greiner, Heinrich Niemann, (Chapter 1.2), Kluwer 2002. Such 3D imagers have a very high depth accuracy. They are mostly limited in their characteristics of speed of acquisition and measurement distance. They all require that no or very few light pulses are emitted before another previously emitted pulse is received and measured. This limitation arises from the risk of confusion of pulses if multiple pulses are on the way between transmitter and receiver at one time. Also, high repetition rate pulses may lead to problems if common optics are used for the emission and reception of pulses, because optical elements may cause partial reflections of pulses. The measurement distance of such devices is limited by the low energy of the pulses they use to maintain eye safety. They then use multiple low-power pulses separated by large time intervals and then average the results to measure a distance for a 3D pixel. Such techniques are not suitable for obtaining fast landscape imaging. In such a technique, a 3D imager should be able to scan the surroundings in nearly all directions.
In other technical fields, some devices are using light at 1.5-μm near-infrared (NIR) wavelength. They are mainly long distance rangefinders or airborne lidars using the relatively eye-safe properties of that wavelength region, as such light is absorbed in the eye's lens. However, it is not possible to generate an image on the basis of such a lidar with a high resolution, at all ranges. Further, the time to acquire a complete frame of the scene is long, especially when the scanned scene is a complete landscape.